1. Field of the Invention
The invention relates to a circuit board and a manufacturing method thereof, and particularly relates to a circuit board where there is no mesh-shaped fiber structure in a dielectric layer on a portion of a dielectric substrate exposed by a circuit pattern and a manufacturing method thereof.
2. Description of Related Art
Generally speaking, a manufacturing process of a circuit board includes steps such as forming a circuit pattern on a substrate, forming a dielectric layer covering the circuit pattern, forming a conductive via in the dielectric layer, and forming another layer of circuit pattern on the dielectric layer, etc. The dielectric layer is usually formed of a resin matrix and a mesh-shaped glass fiber structure in the resin matrix. In the step of forming the dielectric layer covering the circuit pattern, the dielectric layer is usually disposed on the substrate where the circuit pattern is already formed, and a thermal compressing process is performed so that the resin matrix in the dielectric layer is melted to cover the circuit pattern.
However, when the circuit pattern in the circuit board requires a greater thickness (e.g., when the circuit board is applied in a device for vehicles), it is usually challenging to completely fill a region on a portion of the dielectric substrate exposed by the circuit pattern with the melted resin matrix during the thermal compressing process. Alternatively, during the thermal compressing process, it may be challenging to fill the region because the resin matrix in the melted state may be affected by the mesh-shaped glass fiber structure. Thus, there may be pores in the circuit board being formed, so the reliability of the circuit board may be reduced.